Interchangable?

I was just wondering, what all parts, if any, are interchangable between the 300ex, and the 400ex or 250r..?

[moto93]

The wheels are interchangeable.

[oynot400]

I know that there are some parts that are interchangable inbetween the R and 400ex. I would think that if you got a parts catologue and comepaired numbers of what you are looking for you would know for sure. :D

the a arms